Fuel injection pump with means for changing the speed-delivery characteristic thereof



June 11, 1968 w. VOIT 3,387,562

FUEL INJECTION PUMP WITH MEANS FOR CHANGING THE SPEED-DELIVERY CHARACTERISTIC THEREOF Filed Dec. 19, 1966 a 30 v F752 wmvroa 1/1 7 aiL United States Patent 3,387,562 FUEL ENJEQTION PUB/H WITH MEANS FOR CHANGING THE SPEED-DELIVERY CHAR- ACTERISTIC THEREDF Willy Voit, Stuttgart, Germany, assignor to Robert Bosch G.rn.h.H., Stuttgart, Germany Filed Dec. 19, 1966, Ser. No. 602,848 Claims priority, applicatign Germany, Dec. 24, 1965,

5,155 4 Clmms. (Cl. 1t3337) ABSTRACT OF THE DISCLOSURE A fuel injection pump for a multiple cylinder internal combustion engine and including a pumping and distributing member extending through one end of a cylindrical pumping chamber and being reciprocable therein and turnable about its axis so as to suck during its suction stroke fuel into the pumping chamber and to discharge the fuel into a respective cylinder of the engine during the compression stroke, and in which the other end of the pumping chamber is closed by an axially adjustable piston to thus adjust the volume of the pumping chamber independent of the stroke of the pumping and distributing member to change thereby the speed-delivery characteristic of the pump.

Background of the invention It is known that the speed-delivery characteristic of a fuel injection pump does not show a constant delivery of fuel at each pumping stroke during an increase of the number of revolutions of the pump, but that the characteristic shows a small increase of the delivery per stroke or a decrease of the delivered fuel amount. This variation depends on the control of the inlet and outlet passages of the pump and the leakage losses thereof, and these variations are also influenced by the compressibility of the fuel under the influence of the pressure which increase with an increase of the number of revolutions of the pump. The last-mentioned cause is especially great when the fuel injection pressure increases rapidly with the increasing number of revolutions of the pump, which is the case when the fuel pump delivers the fuel to injection hole-type nozzles. The speed delivery characteristic of a fuel injection pump will therefore depend on the construction of the pump and the operation thereof. An adjustment of the desired delivered amount of fuel is usually obtained by an inlet throttle or by a bypass valve control of the injection pump.

A change of the speed-delivery characteristic of the fuel injection pump is usually obtained by special control means which are relatively expensive.

It is an object of the present invention to provide for a method of changing the speed-delivery characteristic of a fuel injection pump in an extremely simple manner.

It is a further object of the present invention to provide for a fuel injection pump in which the speed-delivery characteristic can be changed with means of relative simple construction so that the pump can be manufactured at a reasonable cost and operate trouble-free after extended use.

Summary of the invention The present invention relates to a fuel injection pump having a pumping chamber reciprocable means for alternately sucking fuel into the pumping chamber and for discharging fuel under pressure therefrom, and adjustable means for changing the volume of the pumping chamber independent of said reciprocable means, whereby use is made of the compressibility of the fuel which will result Patented June 11, 1968 that the amount of fuel delivered per stroke of the pump decreases when the feed pressure increases due to an increasing number of revolutions of the pump. The change in the delivered amount, depending on the revolutions of the pump, is therefore adjusted by adjusting the volume of the pumping chamber.

The fuel injection pump according to the present invention mainly includes wall means defining a pumping chamber and having a wall portion adjustable relative to the remainder of the wall means, reciprocable means coopertaing with the pumping chamber and movable between a suction stroke and a compression stroke for sucking fuel into the pumping chamber during the suction stroke and for discharging fuel therefrom under pressure during the compression stroke, and adjusting means cooperating with the adjustable wall portion for changing the position of the latter relative to the remainder of the Wall means and for maintaining the wall portion in any adjusted position, to thus change the volume of the pumping chamber independent of the strokes of the reciprocable means and to change thereby the speed-delivery characteristic of the pump.

The pump may be a fuel injection pump for a multicylinder internal combustion engine, and in this case the reciprocable means are preferably constituted by a hollow cylindrical pumping and distribution member reciprocable along a uction and a compression stroke and rotatable about its axis. In this case the pumping chamber is preferably cylindrical and has a pair of open ends through one of which the pumping and distributing member extends fluid-tightly guided into the pumping chamber, and the movable wall portion of the pumping chamber is preferably constituted by a piston fluid-tightly guided in and closing the other open end of the cylindrical pumping chamber, whereas the means for adjusting and maintaining the axial position of the piston are preferably constituted by an adjusting screw connected to the piston and means for securing the adjusting screw and the piston connected thereto in any adjusted position.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific ernbodiments when read in connection with the accompanying drawings.

Brief description of the drawing tion for different volumes of the pumping chamber.

Description of the preferred embodiment Referring now to the drawing, and more specifically to FIG. 1 of the same in which a fuel injection pump according to the present invention for a multicylinder combustion engine is illustrated in axial cross section, it will be seen that the fuel injection pump includes housing means 1 formed in the Wall thereof with an inlet opening 2 into which a nipple is screwed for connecting the inlet opening to a supply of liquid fuel, not shown in the drawing. The housing 1 is further formed with a stepped bore 3 extending in substantially axial direction through the housing. Guide means in the form of the sleeve 4 are arranged in the lower small diameter portion of the bore 3. The sleeve 5 is formed with one radial bore 5 therethrough which communicates through a passage 6 in the housing wall with the inlet opening 2 of the latter, and with a plurality of radially arranged and angularly diso placed outlet bores 7 which are axially spaced from the bore 6. Only one of the outlet bores 7 is shown in dotted lines in FIG. 1, but it is to be understood that the sleeve 4 is provided with a number of outlet bores corresponding to the number of cylinders of the combustion engine which is to be supplied with fuel from the injection pump shown in FIG. 1. Each of the outlet bores '7 communicates through a channel 8 and a spring loaded valve member 10 with a connecting nipple 9 screwed into a correspondingly threaded bore of the housing 1 through which the pumped fuel is fed into a pressure conduit, not shown in the drawing, to the cylinder of the combustion engine which is coordinated with the respective outlet bore.

The pump includes further reciprocable means in form of an elongated substantially cylindrical pumping and distributing member 11 extending through the guide sleeve 4 and being slidably guided therein. The pumping and distributing member 11 is reciprocated in axial direction along a suction stroke and a compression stroke and also rotated about its axis as indicated by the arrows 12 by means known per se and not forming part of the present invention and including cam means, not shown in the drawing, engaging the bottom end of the member 11 and being driven by the internal combustion engine to which the pump is connected. A compression spring 13 arranged in an upper portion of the bore 3 through the housing 1 abuts with its lower end against an annular member 14 connected to the pumping and distributing member 11 intermediate the ends thereof, and the compression spring 13 is biased to maintain the bottom end of the member 11 in permanent contact with the non-illustrated cam means. The upper end of the compression spring 13 abuts against an annular thrust bearing 15, which in turn abuts against the bottom face of an insert member 16 extending with a threaded portion thereof into the upper end of the axial bore 3 and being threadingly connected to the housing 1.

The insert member 16 is formed with a stepped, coaxing bore having an upper portion provided with an inner screw thread 17 and a lower portion 18 of enlarged diameter to form a shoulder at the upper end of the enlarged diameter. A cylindrical sleeve 19 is coaxially arranged with an upper portion thereof in the enlarged diameter portion 18 of the aforementioned stepped bore through the insert member 16 and the sleeve 19 abuts with its upper end against the aforementioned shoulder. The sleeve extends through the annular thrust bearing into the upper part of the axial bore 3 through the housing 1 and the upper end portion of the pumping and distributing memer 11 extends into the lower portion of the cylindrical sleeve 19 and is fluid-tightly guided therein. The cylindrical sleeve 19 has a radial flange 19a at its upper end which is engaged by the upper end of an annular compression spring 18, which abuts with its lower end against the thrust bearing 15 so as to hold the flange 19a in abutting relationship with the aforementioned shoulder in the insert member 16.

The cylindrical sleeve 19, the upper end of the pumping and distributing member 11 extending through the lower open end of the sleeve 19 in the latter, and a piston 20 fluid-tightly inserted through the upper open end of the sleeve 19 in the latter, comprise wall means defining a pumping chamber 21 and the piston 20 constitutes an adjustable portion of these Wall means permitting to change the volume of the pumping chamber 21 independent of the strokes performed by the pumping and distributing member 11. The piston 20 is coupled in the manner shown in FIG. 1 with the lower end of an adjusting screw 22, screwed into the threaded portion 17 of the axial bore through the insert member 16, and a counter nut 23 screwed onto the outer end of the adjusting screw 22 permits to fixedly hold the adjusting screw 22 in any adjusted position. A cap 24 is screwed onto the upper end of the adjusting screw 22 to protect the latte-r against dirt.

The pumping and distributing member 11 is formed with an axial bore 25, which communicates at the upper end with the pumping chamber 21, and with a plurality of radial inlet passages 26 communicating at the inner ends thereof with the axial bore 25 and adapted to communicate at the outer ends thereof, during rotation of the member 11 about its axis, respectively with the radial bore 5 in the sleeve 4. The member 11 is further formed with a radial outlet passage 27, axially displaced from the passages 26, and communicating at the inner end thereof with the bore 25 and adapted to communicate at the outer end thereof, during rotation of the member 11 about its axis, with a respective one of the outlet bores 7 in the sleeve 4. The number of inlet passages 26 corresponds to the number of outlet bores 7, that is to the number of cylinders in the internal combustion engine to which the pump shown in FIG. 1 is to be connected. The member 11 is at its end portion projecting beyond the sleeve 4 also formed with transverse bores 28 which communicate at the inner ends thereof with the axial bore 25 and the outer ends of which are controlled by a sleeve 29 slidably guided on the bottom end portion of the member 11 and movable in axial direction as indicated by the arrow adjacent thereto.

The above-described pump will operate as follows:

The pumping and distributing member 11 is shown in FIG. 1 in its suction position in which fuel from the inlet opening 2 passes through the channel 6 and the radial bore 5 in one of the radial inlet passages 26 and there with through the central bore 25 in the member 11 into the pumping chamber 21. During the subsequent rotational and upward movement of the pumping and distributing member 11 along its compression stroke, the connection between the bores 5 and 26 are interrupted and a connection is established between the radial bore 27 in the pumping and distributing member 11 and one of the radial bores 7 in the sleeve 4, so that the fuel displaced from the pumping chamber 21 by the pumping and distributing member 11 passes under simultaneous lifting of the valve member 10 into a conduit, not shown in the drawing, which connects the respective nipple 9 with one of the cylinders of the internal combustion engine connected to the pump, until the control sleeve 29 opens the outer ends of the transverse bore 28. The fuel displaced during the remainder of the compression stroke is discharged through the bore 28. After the member 11 reaches its upper dead center position, its movement is reversed and the suction stroke of the pumping and distributing member 11 starts.

The amount of fuel delivered during the above-described pressure stroke of the pumping and distributing member 11 will depend on the number of revolutions of the internal combustion engine to which the pump is connected and therewith to the number of revolutions of the cam driving the member 11. As can be visualized from the diagram of FIG. 2, in which the number of revolutions are entered on the abscissa and the amount of fuel Q delivered per pressure stroke is entered on the ordinate, the amount of fuel delivered per pressure stroke decreases after the number of revolutions per minute surpass a certain value. This relationship, due to the compressibility of the fuel, depends on the volume of the pumping chamber. The diagram of FIG. 2 illustrates two speed-delivery characteristic curves 30 and 31. The curve 31 was established with a pumping chamber having three times the volume of the pumping chamber with which the curve 30 has been plotted. As is evident from FIG. 2, the speed-delivery characteristic curve of a pump can be changed by simply changing the volume of the pumping chamber to obtain in this way a change of the curve to the desired curve configuration. The change of the volume of the pumping chamber can be made with the pump construction according to the present invention by axially shifting the piston 26 by means of the adjusting screw 22, that is with a construction of unobvious simplicity. The end face of the piston 20 forms,

as mentioned before, the adjustable wall portion 20a of the pumping chamber.

By changing the volume of the pumping chamber, it is possible to decrease or diminish the effect of the compressibility of the fuel on the amount of fuel delivered per pressure stroke.

It will be understood that each of the elements de scribed above, or two or more together, may also find a useful application in other types of fuel injection pumps differing from the types described above.

While the invention has been illustrated and described as embodied in a fuel injection pump having a pumping chamber, the volume of which may be varied, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any Way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be protected by Letters Patent is set forth in the appended.

1. In a fuel injection pump for a multi-cylinder internal combustion engine, in combination, wall means defining a pumping chamber, said wall means having a wall portion adjustable relative to the remainder of said wall means; reciprocable means comprising a hollow cylindrical pumping and distributing member extending into said pumping chamber and being fluid-tightly guided therein and being reciprocable along a suction stroke and a compression stroke and rotatable about its axis, said pumping and distributing member being formed in the wall thereof with inlet passage means through which fuel flows into said pumping chamber during said suction stroke and outlet passage means through which fuel flows from said pumping chamber into the respective cylinder of the internal combustion engine during the compression stroke; and

adjusting means cooperating with said adjustable wall portion for changing the position of the latter relative to the remainder of said wall means and for maintaining that adjustable wall portion in any adjustable position to thus change the volume of the pumping chamber independent of the strokes of said reciprocable means to change thereby the speed delivery characteristic of said 2. In a fuel injection pump as defined in claim 1 and including housing means formed with an axial bore therethrough, guide means at one end portion of said bore for guiding said pumping and distributing member in axial direction along its suction and compression strokes, said guide means being formed with an inlet opening adapted to communicate with said inlet passage means during said suction stroke and a plurality of outlet openings adapted to communicate with said outlet passage means during said compression stroke, said wall means defining said cylindrical pumping chamber include a cylindrical member, coaxially arranged in said axial bore of said housing means axially spaced from said guide means, a threaded insert extending partly into said axial bore from the other end thereof and being threadingly connected to said housing means, said insert being formed with an internally threaded axial bore therethrough and said adjusting means being arranged in and threadingly connected to said internally threaded axial bore of said insert.

3. In a fuel injection pump as defined in claim 1, wherein said wall means define a cylindrical pumping chamber having a pair of opposite open ends, and wherein said adjustable wall means comprises a piston fluid-tightly guided in said cylindrical pumping chamber and closing one of said open ends thereof, said reciprocable means extending through the other open end into the pumping chamber, and said adjusting means being connected to said piston for adjusting the axial position of the latter relative to said one end of said pumping chamber and for maintaining said piston in any adjusted position.

4. In a fuel injection pump as defined in claim 3, wherein said adjusting means include an adjusting screw connected to said piston.

References Cited UNITED STATES PATENTS 204,747 6/1878 Maxim 10337 957,451 5/1910 Willet 10337 1,993,369 3/1935 Goldberg 103-37 2,047,167 7/1936 Heller 230--21 2,055,578 9/1936 Hurst 103-37 ROBERT M. WALKER, Primary Examiner.

LAURENCE V. EFNER, Examiner. 

